The present invention relates to a polymer composition comprising a polymer and an anti-static composition. In particular, the present invention relates to a polymer composition comprising a polymer and an anti-static composition, wherein the anti-static composition comprises at least two components having different properties relative to each other. The polymer composition may be used in packaging applications.
Polymers have an extremely wide field of applications. In the food industry the use of polymers for the manufacture of food containers is important. In particular, polymers may be used to manufacture small food containers in which food products may be stored.
After the manufacture of food containers and the like, it is known that static charge may build up on the polymer surface. This static charge attracts dust and other fine particles. If such particles settle on a polymeric food container or similar packaging the container will appear dirty and will be less appealing to purchasers of the food. There is also the possibility of food contamination.
To overcome the problems of static build up on polymers in the food and other industries, anti-static (antistat) compositions have been provided. A good antistat composition dissipates or reduces static charge on a polymer over a long period. In the field of packaging, it is desirable that the antistat properties remain for the life time of the packaged product.
Antistat protection is typically obtained by incorporating an anti-static composition or compound into a polymer. The anti-static composition or compound may be incorporated into the polymer during the processing or production of the polymer, for example during the injection moulding of the polymer.
Conventional anti-static compositions of the prior art are distilled monoglycerides or mono-diglycerides derived from vegetable oils e.g. soya bean and rape seed, and animal fats. These anti-static compositions have been particularly recommended for incorporation into polypropylene and, in addition, have been particularly recommended for incorporation into injection moulded polymers.
Because of the derivation of the above conventional anti-static compositions they most commonly have a fatty acid profile that is a blend of palmitic (C16) acid and stearic (C18) acid.
A typical prior art teaching is provided by JP-A-01263135 which discloses polyolefins containing anti-static agents composed of xe2x89xa72 A1OCH2CH(OA2)xe2x80x94CH2OA3, wherein A1-3=H,COR; Rxe2x95x90C9-21 alkyl or alkenyl, xe2x89xa71 of A1-3 is COR.
JP-A-08134289, JP-A-63213538, JP-A-63056545 and JP-A-07331230 disclose mixtures of glycerides and amine based compounds. These documents teach that these compositions have anti-static properties. To achieve their anti-static properties these compositions require the presence of the amine based compound. Legislation and consumer pressure provides that such amine based compounds should be present at low levels in food applications, or, if possible, completely excluded. However, the above prior art documents require the presence of amine based compounds to exhibit an anti-static effect.
The prior art anti-static compositions may provide acceptable results in some applications. However, in demanding applications, for example in the use of block copolymer polypropylene, the prior art anti-static compositions do not provide reliable results.
Furthermore, prior art antistats may also be disadvantageous because they may be incompatible with the polymer into which they are incorporated or with which they may be contacted. For example, the electronics industry commonly uses polycarbonates as a substrate and/or carrier for electronic components. However, nitrogen based or ionic anti-static compounds, which are commonly used, may corrode polycarbonate materials.
The present invention addresses the problems of the prior art anti-static compounds and compositions, namely their poor performance in use with some polymers and/or in some applications.
The present invention aims to overcome the problems of the prior art.
According to a first aspect of the present invention there is provided use of an anti-static composition for the manufacture of a polymer composition, e.g., the present invention can provide an anti-static composition, as well as a polymer composition including the anti-static composition; wherein the anti-static composition comprises at least a first component (xe2x80x9ccomposition Ixe2x80x9d) and a second component (xe2x80x9ccomposition IIxe2x80x9d); wherein the first or second component inhibits the crystallisation of the other respective component; wherein at least the other respective component is an anti-static component; and wherein the anti-static composition is contacted with a polymer to form the polymer composition; with the proviso that if the anti-static composition consists solely of composition I and composition II, the anti-static composition is prepared by any one of: (i) integrated blending; or (ii) dry blending. Thus, the present invention also provides a method for preparing an anti-static composition comprising integrated or dry blending of compositions I and II, as well as a method for preparing the polymer composition comprising contacting the anti-static composition with the polymer to form the polymer composition.
Therefore, according to a second aspect of the present invention there is provided a method of preparing a polymer composition comprising the steps of a) providing an anti- static composition comprising at least a first component and a second component; wherein the first or second component inhibits the crystallisation of the other respective component; and wherein at least the other respective component is an anti-static component; and b) contacting the anti-static composition with a polymer to form the polymer composition; with the proviso that if the anti-static composition consists solely of composition I and composition II, the anti-static composition is prepared by any one of: (i) integrated blending; (ii) dry blending.
According to a third aspect of the present invention there is provided a polymer composition comprising: a polymer; and an anti-static composition; wherein the anti-static composition comprises at least a first component and a second component; wherein the first or second component inhibits the crystallisation of the other respective component; and wherein at least the other respective component is an anti-static component; with the proviso that if the anti-static composition consists solely of composition I and composition II the anti-static composition is prepared by any one of: (i) integrated blending; (ii) dry blending.
According to a fourth aspect of the present invention there is provided an integrated pellet comprising a polymer and an inventive anti-static composition; or, comprising an inventive polymer composition.
According to a fifth aspect of the invention, there is provided a container comprising an inventive polymer composition or comprising a polymer composition prepared in accordance with the methods or uses described herein.
These and other objectives and embodiments are disclosed or are obvious from and encompassed by the following Detailed Description.
As discussed above, the present invention entails, for instance, according to a first aspect, use of an anti-static composition for the manufacture of a polymer composition, e.g., the present invention can provide an anti-static composition, as well as a polymer composition including the anti-static composition; wherein the anti-static composition comprises at least a first component (xe2x80x9ccomposition Ixe2x80x9d) and a second component (xe2x80x9ccomposition IIxe2x80x9d); wherein the first or second component inhibits the crystallisation of the other respective component; wherein at least the other respective component is an anti-static component; and wherein the anti-static composition is contacted with a polymer to form the polymer composition; with the proviso that if the anti-static composition consists solely of composition I and composition II, the anti-static composition is prepared by any one of: (i) integrated blending; or (ii) dry blending. Thus, the present invention also provides a method for preparing an anti-static composition comprising integrated or dry blending of compositions I and II, as well as a method for preparing the polymer composition comprising contacting the anti-static composition with the polymer to form the polymer composition.
Likewise, as discussed above, according to a second aspect, the present invention provides a method of preparing a polymer composition comprising the steps of a) providing an anti-static composition comprising at least a first component and a second component; wherein the first or second component inhibits the crystallisation of the other respective component; and wherein at least the other respective component is an anti-static component; and b) contacting the anti-static composition with a polymer to form the polymer composition; with the proviso that if the anti-static composition consists solely of composition I and composition II, the anti-static composition is prepared by any one of: (i) integrated blending; (ii) dry blending.
Similarly, as discussed above, according to a third aspect, the present invention provides a polymer composition comprising: a polymer; and an anti-static composition; wherein the anti-static composition comprises at least a first component and a second component; wherein the first or second component inhibits the crystallisation of the other respective component; and wherein at least the other respective component is an anti-static component; with the proviso that if the anti-static composition consists solely of composition I and composition II the anti-static composition is prepared by any one of: (i) integrated blending; (ii) dry blending.
The present invention overcomes the problems of the prior art by providing an anti-static composition which is effective over the lifetime or a substantial part thereof of a polymer article.
It will be appreciated that the use of antistat compositions of the present invention are not limited to the field of food packaging and accordingly the present application is not limited thereto. For example, the antistat compositions also have applications in, for example:
electronics industryxe2x80x94here the build up of static charges are to be avoided because of the damage which may be caused to electronic components e.g. semi-conductors by the discharge of the static charge;
aerospace industryxe2x80x94here build up static charge may attract dust/dirt and compromise delicate components
automotive industryxe2x80x94here build of static charge may attract dust/dirt and detract from the appearance of vehicles and/or components thereof;
non-food packaging applicationsxe2x80x94for example, in the paint industry, build of static charge on a paint container may result in attraction of dust/dirt. The dust/dirt may contaminate the paint on introduction thereof into the container and/or may render the container unappealing to the purchaser;
extreme environmentsxe2x80x94here environments with aggressive, in particular explosive atmospheres are vulnerable to static charge build up. If a static charge discharges in an explosive atmosphere, detonation of the atmosphere may result.
In the present specification, the term xe2x80x9cintegrated blendingxe2x80x9d means blending the components when all the components are in the liquid phase.
In the present specification, the term xe2x80x9cdry blendingxe2x80x9d means blending the components when at least one of the components is a phase other than the liquid phase.
The above aspects of the present invention are advantageous as they overcome the problems associated with the prior art.
In the present specification, composition I refers to a composition consisting of a distilled mono-glyceride prepared from edible, fully hydrogenated lard or tallow, the composition having the following specification:
In the present specification, composition H refers to a composition consisting of a distilled mono-glyceride prepared from edible, distilled, reaction product of lauric acid and glycerol, the composition having the following specification:
An anti-static composition contained in a polymer composition is believed to migrate to the surface of the polymer composition. At the surface the anti-static composition attracts water to the surface. The attracted water forms a conductive layer which dissipates static charge and/or prevents accumulation of static charge. We also believe that the properties of the anti-static compositions of the prior art are inhibited by the crystallisation of the composition at the surface of the polymer. Thus the problems of the prior art have been overcome in the present invention by providing an anti-static composition comprising at least a first component and a second component, wherein the first or second component inhibits the crystallisation of the other respective component and wherein at least the other respective component is an anti-static component
Crystallisation of an anti-static component in an antistat applied to a polymer may also result in clouding or hazing of the polymer. The present invention is also advantageous in that by providing two components, wherein one of which inhibits the crystallisation of the other, clouding of the polymer may be reduced or prevented.
In the present specification, the term xe2x80x9ccontacted with a polymerxe2x80x9d means that the anti-static composition is brought into contact with the polymer or is mixed and/or blended and/or integrated with the polymer and/or is incorporated into the polymer. The polymer composition containing the polymer and the anti-static composition may then, if necessary, be further processed, for example the polymer composition may be melted. Optionally the melt may be extruded and subsequently cooled.
The term xe2x80x9cblendingxe2x80x9d with respect to contacting the anti-static composition with the polymer includes
i) dry blending of the components to be blended, for example by mixing the components in a powdered form and, optionally, subsequently extruding them; and
ii) dry blending the polymer in a pellet form with the anti-static composition, for example by mixing the polymer and anti-static composition in a pellet and a powdered form, respectively and, optionally, subsequently extruding them.
In a preferred embodiment the anti-static composition and polymer are integrated. This may be achieved by melting the polymer and/or the anti-static composition and combining the polymer and anti-static composition. Optionally, the melt of the two materials may be extruded. In a preferred embodiment the integrated product is in a pellet form.
Thus, according to a fourth aspect of the present invention there is provided an integrated pellet comprising a polymer, and an anti-static composition.
Preferably, a container comprising a polymer composition in accordance with the present invention exhibits anti-static properties within 24 hours of its date of manufacture and maintains those properties for a prolonged periodxe2x80x94such as for at least 5 days, preferably at least 10 days, preferably at least 14 days, preferably at least 20 days, preferably at least 40 days, preferably at least 60 days, preferably at least 80 days, preferably at least 100 days, preferably at least 150 days, preferably at least 200 days. Such a container, or indeed any other polymer article comprising the polymer composition, avoids the build up of static charge during the manipulation and/or treatment and/or shipping of the container. This is advantageous because a static charge may attract dust which would, for example,
reduce the adherence of a label which is to be applied further down a production line;
be incorporated into or entrappsed by a subsequently applied print or paint layer and be visible through the layer; or
pollute the inside of the container.
By the term xe2x80x9cexhibits anti-static propertiesxe2x80x9d we mean that when the polymer composition is in the form of a plaque having a thickness of 1.0 mm and contains 0.6 wt % of anti-static composition based on the total weight of the polymer composition, the polymer composition has a measurable static delay time when measured in accordance with the Static Delay Time Protocol given in the Examples.
Thus according to a fifth aspect of the present invention there is provided a container comprising a polymer composition described above or comprising a polymer composition prepared in accordance with a method or use described above.
Preferably, the polymer is selected from polymerisation or copolymerisation products of monomers selected from those disclosed in U.S. Pat. No. 5,679,816, namely ethylenically and/or acetylenically unsaturated monomers having from 2 to 20 carbon atoms. Preferred monomers of those disclosed include C2-10 alpha-olefins including ethylene, propylene, isobutylene, 1-butene, 1-hexene, 4-methyl-1-pentene, and 1-octene. Other preferred monomers include carbonates, xcex1-olefin rubber, butadiene, ethyleneterephthalate, vinylchloride, ethylene propylene rubber (EPR), acrylonitrile, vinylcyclohexene, vinylcyclohexane, styrene, C1-4 alkyl substituted styrene, tetrafluoroethylene, vinylbenzocyclobutane, ethyl-idenenorbornene, piperylene, 1,4-hexadiene, methyl-1,4-hexadiene and 7-methyl-1,6-octadiene, derivatives and mixtures thereof. Thus, the polymer can be a polyethylene, such as low density polyethylene (LDPE), linear low density polyethylene (LLDPE), ultra low density polyethylene (ULDPE), very low density polyethylene (VLDPE), high density polyethylene (HDPE), e.g., an HDPE homopolymer, single site catalyst polyethylene (SSCPE); or, polypropylene, such as a polypropylene block copolymer or oriented polypropylene, and the like.
Preferably, the polymer is selected from polymerisation and copolymerisation products of propylene, xcex1-olefin rubber, styrene, derivatives and mixtures thereof.
Preferably, the polymer is a thermoplastic polyolefin (TPO). TPOs have extensive applications, in particular in the automotive industry.
The polymer may be any form of polymer. The term polymer includes but is not limited to, homopolymers, copolymers, such as for example, block, graft, random and alternating copolymers, terpolymers, etc. and blends and modifications thereof. Furthermore, the term polymer includes all possible geometrical configurations of the polymer. These configurations include, but are not limited to isotactic, syndiotactic and atactic i.e. random symmetries.
Preferably, the polymer is a copolymer. Preferably, the monomer constituents of the copolymer are selected from the monomer units listed above. The copolymer may be a random copolymer, a branched copolymer or a block copolymer (sometimes referred to as a impact copolymer or a heterophasic copolymer). Preferably, the copolymer is a block copolymer.
Preferred copolymers include copolymers of ethylene and 1-butene; ethylene and 1-hexene; ethylene and 1-octene; styrene and acrylonitrile; styrene, acrylonitrile and butadiene; high impact styrene and acrylonitrile; high impact styrene, acrylonitrile and butadiene.
Preferably, the copolymer includes monomer units selected from propylene, ethylene propylene rubber (EPR), acrylonitrile, styrene, derivatives and mixtures thereof. In a particularly preferred embodiment the polymer is polypropylene block copolymer.
The polymer may be copolymer of propylene and ethylene. The polymer may be a copolymer comprising at least 70 wt % propylene and no more than 30 wt % ethylene. The polymer may be a copolymer comprising propylene and no more than 40 wt % EPR.
The polymer may be a mixture of the polymerisation or copolymerisation products of any of the above monomers.
In the present specification reference has been made to polymers and to polymer compositions comprising anti-static compositions. In addition, the present invention also encompasses polymerisable compositions which comprise the respective monomers and monomer compositions comprising anti-static compositions. Such polymerisable compositions comprising anti-static compositions could be polymerised to obtain the respective polymers or polymer compositions referred in the present specification.
The anti-static composition of the present invention may comprise any compound or mixture of compounds provided the anti-static composition meets the criteria of the present invention as described above.
The at least two components of the anti-static composition may be discrete from each other. Alternatively, the two components may be linked. In this latter embodiment, the two components may be two constituents of the same compound.
Preferably, the at least two components of the anti-static composition are discrete from each other.
When the at least two components of the anti-static composition are discrete from each other, the at least two components may be obtained from a common source material. The common source material may be selected from coconut oil, palm kernel oil including Babassu oil, Cohune oil, Murumuru oil, Ouricuri oil and Tucum oil, mixtures and derivatives thereof.
Preferably, the common source material contains at least two glycerides having different fatty acid chain lengths. More preferably, the at least two glycerides having different fatty acid chain lengths which differ in length by at least two carbons, yet more preferably by at least four carbons. Suitable common source materials include coconut oil, palm kernel oil including Babassu oil, Cohune oil, Murumuru oil, Ouricuri oil and Tucum oil, butterfat, herring oil, menhaden oil, mixtures and derivatives thereof
When the at least two components of the anti-static composition are discrete from each other, the at least two components may be combined by blending.
The term xe2x80x9cblendingxe2x80x9d with respect to combining the at least two components includes
i) dry blending of the components to be blended, for example by mixing the components in a powdered form;
ii) spray blending, for example by blending the components in a fluid form and subsequent spraying. This may be achieved by melting of the components or by dissolving them or suspending them in a carrier material;
iii) blending and milling of the components to be blended;
iv) blending and flaking of the components to be blended;
v) forming the components into pellets on a cooling band;
vi) integrating the components. This may be achieved by providing each of the components in fluid form, preferably in a liquid form, and mixing the components.
The mixed components may optionally be cooled;
vii) any combination of i) to vi) above;
viii) optionally treating the product after any one of i) to vii) above to form a liquid, block, powder, pellet or flake.
In the above blending processes the components may each be in any one of the following forms, independently of each other: liquid, block, powder, pellet and flake.
Preferably, each of the two components of the anti-static composition are independently selected from monoglycerides having a fatty acid chain length of no greater than 14 carbons, monoglycerides having a fatty acid chain length of from 4 to 14 carbons, monoglycerides having a fatty acid chain length of from 6 to 14 carbons, monoglycerides having a fatty acid chain length of from 8 to 14 carbons, monoglycerides having a fatty acid chain length of from 10 to 14 carbons, monoglycerides having a fatty acid chain A length of 12 carbons including the reaction product of glycerol and lauric acid (preferably the lauric acid is obtained from coconut oil, palm kernel oil including Babassu oil, Cohune oil, Murumuru oil, Ouricuri oil and Tucum oil), monoglycerides having a fatty acid chain length of from 16 to 24 carbons, monoglycerides having a fatty acid chain length of from 16 to 22 carbons, monoglycerides having a fatty acid chain length of from 18 to 22 carbons, monoglycerides having a fatty acid chain length of from 18 to 20 carbons, animal fats, including lard and tallow, vegetable oils including rape seed oil, soya bean oil, palm oil, mixtures and derivatives thereof.
Preferably, the first component is selected from monoglycerides having a fatty acid chain length of from 4 to 14 carbons, monoglycerides having a fatty acid chain length of from 6 to 14 carbons, monoglycerides having a fatty acid chain length of from 8 to 14 carbons, monoglycerides having a fatty acid chain length of from 10 to 14 carbons, monoglycerides having a fatty acid chain length of 12 carbons including the reaction product of glycerol and lauric acid, mixtures and derivatives thereof. Preferably the lauric acid is obtained from coconut oil, palm kernel oil including Babassu oil, Cohune oil, Murumuru oil, Ouricuri oil and Tucum oil, mixtures and derivatives thereof.
Preferably, the second component is selected from monoglycerides having a fatty acid chain length of from 16 to 24 carbons, monoglycerides having a fatty acid chain length of from 16 to 22 carbons, monoglycerides having a fatty acid chain length of from 18 to 22 carbons, monoglycerides having a fatty acid chain length of from 18 to 20 carbons, animal fats, including lard and tallow, vegetable oils including rape seed oil, soya bean oil, palm oil, mixtures and derivatives thereof.
Preferably, the first component and/or the second component is at least a glycerol ester (i.e. a glyceride) preferably, each of the first component and the second component is at least a glyceride.
More preferably, the first component and/or the second component is at least a monoglyceride. Yet more preferably, each of the first component and the second component is at least a monoglyceride.
In a further preferred embodiment the first component is a monoglyceride having a fatty acid chain length of 8 carbons and/or a monoglyceride having a fatty acid chain length of 10 carbons and the second anti-static component is a monoglyceride having a fatty acid chain length of 14 carbons. In a further preferred embodiment the first component is a monoglyceride having a fatty acid chain length of 12 carbons and the second anti-static component is a monoglyceride having a fatty acid chain length of 18 carbons.
When a glyceride is utilised as the anti-static component, crystallisation may be prevented/inhibited by providing a component which prevents the glyceride from switching from xcex1-form to xcex2-form. Such a component may be selected from the class of products known as xcex1-tending products. Thus in a preferred embodiment, the anti-static component is a glyceride, more preferably a mono-glyceride, and the crystallisation inhibiting component is an ax-tending product.
Preferably, the xcex1-tending product is selected from propylene glycol esters, for example GRINSTED PGMS SPV(trademark) available from Danisco Ingredients, Denmark, polyglycerol esters, for example GRINSTED PGE 55(trademark) available from Danisco Ingredients, Denmark, mixtures and derivatives thereof.
Preferably, the first component comprises at least 15 wt % of the anti-static composition. Preferably, the first component comprises at least 20 wt % of the anti-static composition.
Preferably, the second component comprises at least 30 wt % of the anti-static composition. Preferably, the second component comprises at least 40 wt % of the anti-static composition.
Preferably, the anti-static composition comprises at least 20 wt % of the first component. More preferably, the anti-static composition comprises at least 30 wt %, more preferably at least 50 wt % of the first component.
Preferably, the anti-static composition comprises at least 20 wt % of the second component. More preferably, the anti-static composition comprises at least 30 wt %, more preferably at least 50 wt % of the second component.
In a preferred embodiment the anti-static composition comprises 35 wt % of the first component and 65 wt % of the second component or vice versa. In yet another preferred embodiment the anti-static composition comprises 50 wt % of the first component and 50 wt % of the second component.
In the process or use of the present invention the anti-static composition may be contacted with the polymer by first combining the anti-static composition with a first polymer to form a polymer master batch composition. Preferably, the anti-static composition comprises at least 5 wt % of the polymer master batch composition. The polymer master batch composition is then combined with a second polymer and the mixture treated to form the polymer composition. Preferably, the polymer composition so formed is substantially homogenous.
The first polymer and the second polymer may be the same.
Preferably the polymer composition is substantially homogenous.
By xe2x80x9csubstantially homogenousxe2x80x9d it is meant that for any part of the polymer composition comprising x wt % thereof, that part of the polymer composition contains xxc2x10.2x wt % of the total amount of a given component of the polymer composition. Preferably, that part of the polymer composition contains xxc2x10.1x wt % of the total amount of the given component. More preferably, that part of the polymer composition contains xxc2x10.05x wt % of the total amount of the given component. Yet more preferably, that part of the polymer composition contains xxc2x10.02x wt % of the total amount of the given component.
Preferably, the given component of the polymer composition is the anti-static composition.
Polymers are prepared by polymerising one or more types of polymerisable monomers, such as by emulsion polymerisation, solution polymerisation, suspension polymerisation, gas phase polymerisation or bulk polymerisation.
The monomer(s) may be polymerised in the presence of optional ingredients such as any one or more of emulsifiers, stabilisers, anti-oxidants, surface active agents, slip agents, further anti-static compositions, initiators (such as photoinitiators), inhibitors, dispersants, oxidising agents, reducing agents, viscosity modifiers, catalysts, binders, activators, accelerators, tackifiers, plasticizers, saponification agents, chain transfer agents, cross-linking agents, surfactants, fillers, pigments, dyes, metal salts, solvents, mixtures and derivatives thereof. The optional ingredients listed above that can be used in the present invention may be any of those commonly used in the art.
Alternatively and/or in addition an optional ingredients may be contacted with/added to the polymer after polymerisation. Suitable optional ingredients include any one or more of emulsifiers, stabilisers, acid scavenger, anti-oxidants, surface active agents, slip agents, further anti-static compositions, dispersants, viscosity modifiers, tackifiers, plasticizers, surfactants, fillers, pigments, dyes, metal salts, solvents, mixtures and derivatives thereof. The optional ingredients listed above that can be used in the present invention may be any of those commonly used in the art.
Preferably, the anti-oxidant is a phenolic anti-oxidant.
Preferably, the acid scavenger is calcium stearate or calcium lactate.
By way of example, the surfactants and dispersants can be salts of fatty rosin and naphthenic acids, condensation products of naphthalene sulphonic acid and formaldehyde of low molecular weight, carboxylic polymers and copolymers of the appropriate hydrophile-lipophile balance, higher alkyl sulphates, such as sodium lauryl sulphate, alkyl aryl sulfonates, such as dodecylbenzene sulfonate, sodium or potassium isopropylbenzene sulfonates or isopropylnaphthalene sulfonates; sulfosuccinates, such as sodium dioctylsulfosuccinate alkali metal higher alkyl sulfosuccinates, e.g. sodium octyl sulfosuccinate, sodium N-methyl-N-palmitoyl-taurate, sodium oleyl isethionate, alkali metal salts of alkylarylpolyethoxyethanol sulfates or sulfonates, e.g.. sodium t-octylphenoxy-polyethoxyethyl sulfate having 1 to 5 oxyethylene units. Typical polymerisation inhibitors that can be used include hydroquinone, monomethyl ether, benzoquinone, phenothiazine and methylene blue.